1. Field of the Invention
The present invention relates to a multiplex transmission system for multiplexing information used for processing abnormality in load control (hereinafter referred to as abnormality processing control specification information: abnormality PCSI) and used in normal load control (hereinafter referred to as normality processing control specification information: normality PCSI) through a multiplex transmission network connected to load control units (LCUs) capable of controlling loads connected thereto. In the present invention, the load refers to electric components (e.g. a lamp, and air conditioner, water heater, etc.) mounted in a motor vehicle (e.g. bus, motor car, passenger vehicle).
2. Description of the Related Art
One example of the multiplex transmission system used for load control has been proposed in FIG. 10.
Such a kind of a previously known system as shown in FIG. 10 has been proposed.
A multiplex transmission system 5 includes a master load control unit (master LCU)1 and at least one slave load control units (slave LCUs) 2 and 3 (two in FIG. 10) which are interconnected through a multiplex transmission network 4.
The master LCU 1 and the slave LCUs 2 and 3 incorporate storage means 1a, 2a and 3a for receiving or storing abnormality PCSI is shown in FIG. 11. When communication abnormality occurs in the multiplex transmission network 4 owing to failure such as wire braking, the multiplex transmission system controls the processing (specifically, output control after wire breaking) in accordance with abnormality PCSI maintaining the control state (specifically, output before wire braking).
The storage means 1a, 2a and 3a store the abnormality PCSI, which are those for loads 2b, 2c and 3c, in its state multiplexed through the multiplex transmission network 4.
The normality PCSI or abnormality PCSI by the storage means 1a, 2a and 3a is updated by writing new normality PCSI or abnormality PCSI into the storage means 1a of the master LCU 1 from e.g. an external writing terminal connected to the master LCU 1.
It should be noted that the PCSI for the loads 2b, 2c, 3b, 3c includes the kind of the load and control method (e.g. abnormality processing of the blinking period of the lamp, lighting illuminance and door linkage lighting, power supply for air conditioner).
Setting a select switch (S1)6a or (S2)6b permits the load (L1)2b or (L2)2c to be controlled selectively through the slave LCU 2, and also permits the load (L3)3b or (L4)3c to be controlled selectively through the slave LCU 3.
In the multiplex transmission system as seen from FIG. 12, during the normal operation, the master LCU 1 falls in a transmission mode to transmit the normality or abnormality PCSI during a prescribed time (a sec in FIG. 12). At the same time, each slave LCU 2 or 3 falls in a reception mode during a prescribed time (a+.alpha. in FIG. 12) using an incorporated timer to receive the normality or abnormality PCSI and stores it on its storage means 2a or 3a.
Subsequently, the slave LCU 2 falls in the transmission mode to transmit the control information during a prescribed time (b sec in FIG. 12). At the same time, the master LCU 2 and slave LCU 3 fall in the reception mode during a prescribed time (b+.alpha. sec) using incorporated timers, respectively to receive the abnormality or normality PCSI from the control unit 2 and store it on the storage means 1a and 3a, respectively.
Likewise, the slave LCU 3 falls in the transmission mode to transmit the control information during a prescribed time (c sec in FIG. 12). At the same time, the master LCU 1 and slave LCU 2 fall in the reception mode during a prescribed time (c+.alpha. sec) using incorporated timers, respectively to receive the PCSI from the control unit 2 and store it on the storage means 2a and 1a, respectively.
In the conventional multiplex transmission system, the recovery processing from the abnormality state (e.g. succession of the previous state, or forcible ON or OFF attendant on control on the abnormality processing) can be performed as follows.
The master LCU 1 preferentially falls in the transmission mode to start abnormal mode communication. The multiplexing of the normality or abnormality PCSI received or previously stored by the master LCU 1 as shown in FIG. 12 is executed for the other slave LCUs 2 and 3 and this information is held in the corresponding storage means 2a and 3a. In this case, the slave LCU 2 controls the loads 2b and 2c connected to itself on the basis of the normality or abnormality PCSI multiplexed by the forcible abnormal communication. The slave LCU 3 also controls the loads 3b and 3c connected to itself on the basis of the normality or abnormality PCSI multiplexed by the forcible abnormal communication.
Additionally, it should be noted that the abnormality occurring in the multiplex transmission system includes operation abnormality of the LCU due to communication abnormality in the multiplex transmission network, breaking of a power source, etc.
However, where the communication abnormality occurs in the multiplex transmission network 4 owing to e.g. wire braking, the conventional multiplex transmission system 5 described above, as shown in FIG. 11, abnormality processing control (concretely, output control after wire braking) is effected in accordance with the abnormality PCSI to maintain the control state before the abnormality occurs (concretely, output before wire braking). Therefore, the control of maintaining the previous state is similarly effected for also the load giving inconvenience when the previous state is maintained. Specifically, for the water heater for which power supply is "on" before the communication abnormality occurs, the control of maintaining the previous state i.e. "on" state is effected, thus giving possibility of causing fire. In short, the default processing (concretely, succession of the previous state or forcible `on`/`off` processing)is not suitably set for each load.
Where the abnormality or normality PCSI stored in the storage means 1a, 2a and 3a in the conventional multiplex transmission system 5 is updated, the normality or abnormality PCSI to be updated is stored in the storage unit 1a of the master LCU 1 from an external writing terminal connected thereto. Therefore, in the multiplex transmission system, loads having various control information may be changed by the user's convenience. When abnormality occurs in such a multiplex transmission system, the default processing attendant on the abnormality processing cannot be effected easily.
Further, since the multiplex transmission system using new abnormality PCSI cannot be easily designed at a place remote from the multiplex transmission system at issue, the multiplex transmission system cannot be updated easily, quickly, safely and surely.
In the abnormality processing control method and abnormality processing apparatus used in such a conventional multiplex transmission system 5, in the recovery processing from the abnormal state, the master LCU 1 preferentially falls into the transmission mode to start the abnormal mode communication so that the multiplexing of the abnormality PCSI received or previously stored by the master LCU 1 is forcibly effected for other LCUs (slave LCUs 2 and 3). Thus, the unnecessary abnormal mode communication during the recovery from the abnormal state is also carried out for the LCU(s) which operates normally.
For this reason, the normal load control or multiplex processing which has been carried out in to the LCU which operates normally will be stopped inadvertently.
In short, since the load control or multiplex processing being normally executed is stopped during the recovery from the abnormal state and carried out on the basis of the abnormal mode communication, the recovery processing of the load control or multiplexing cannot be carried out with high reliability and assurance.